Table 1.

Animal studies of the gut microbiota in T1D.

Reference	Authors	Year of Study	Animal Model	Study Findings
[74]	Wu et al.	2021	NOD/ltj T1D mice vs. ICR mice	Decreased microbiota diversity and community richness were shown in animals before the onset of T1D. T1D was associated with increased Firmicutes, Proteobacteria, and Deferribacteres phyla abundance. Coprococcus 2, Lachnoclostridium_5, and Lachnospariceae_FCS020 genera (Firmicutes Phylum) were dominant in T1D, and their levels positively correlated with blood neutrophil ratios.
[75]	Ma et al.	2020	Streptozotocin-induced T1D rats vs. control	Firmicutes and Bacteroidetes are the dominant phyla in T1D rats. Pathogenic bacteria are abundant in T1D rats, while beneficial bacteria are reduced compared to control. Butyricicoccus and Allobaculum produce SCFAs and protect intestinal barrier function. Imbalance of gut microbiota causes reduction of SCFAs and intestinal inflammation.
[76]	Prasad et al.	2019	Angiotensin-converting enzyme 2 (ACE2) deficient T1D Akita mice vs. control	Increased Firmicutes and Bacteroidetes in the gut of ACE2−/−Akita mice ACE2 loss induced gut barrier permeability. Dysbiosis in the gut promoted the development of diabetic nephropathy.
[77]	Patterson et al.	2015	Streptozotocin (STZ) induced T1D in Sprague–Dawley rats (over time) vs. control	Animals with T1D have decreased microbial diversity and differential expression of microbiota. T1D onset was associated with an increase in Bacteriodetes: Firmicutes ratio. Increased lactic acid-producing bacteria (Bifidobacterium and Lactobacillus) was associated with late-stage T1D progression.
[78]	Hara et al.	2012	Virus-induced T1D rats vs. control	Virus-induced T1D animals expressed increased levels of Bifibacterium and Clostridium species and were reduced following antibiotic administration.
[79]	Roesch et al.	2009	Bio-breeding diabetes-prone (BB-DP) vs. bio-breeding diabetes-resistant (BB-DR) rats	BB-DR rats had more Lactobacillus and Bifidobacterium genera vs. BB-DP. Increased levels of 9 genera were also demonstrated in BB-DP rats in correlation with the onset of diabetes.
[80]	Brugman et al.	2006	Diabetic BB-DP rats before and after the onset of diabetes in the presence and absence of antibiotics	Rats protected from diabetes had a lower amount of Bacteroides species compared to rats with high levels. Modulation of microbiota by antibiotics reduced the incidence of T1D and delayed its onset.